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In the healthy gut, NF-κB is a critical factor of the intestinal immune system, whereas inflammatory bowel diseases are associated with chronic activation of NF-κB. Previous studies indicated that coffee induces nuclear translocation of NF-κB in macrophages, an effect attributed to roasting products. In the present work, coffee extract or roasting products induced nuclear translocation of NF-κB in macrophages, Caco-2 cells, and primary human intestinal microvascular endothelial cells (up to fivefold, p0.001). Since the effect clearly depended on the cell type, ex vivo experiments were performed with intact human gut tissue from biopsies. The uniformity of the specimens and tissue viability during ex vivo incubation for up to 2 h were verified. Roasting products led to a concentration dependent significant increase of nuclear translocation of NF-κB in human gut tissue (up to 2.85 fold increase, p=0.0321), whereas coffee extract induced a trend towards higher nuclear NF-κB concentration. NF-κB activation in macrophages and Caco-2 cells by roasting products was significantly blocked by co-incubation with catalase (p=0.011 and p=0.024) indicating involvement of H(2)O(2)-signaling. Monitoring of extracellular H(2)O(2) indicated that roasting products in coffee constantly generate H(2)O(2) by spontaneous oxygen reduction, which is only partially detoxified by cellular antioxidative systems. Thus, it can be concluded that ex vivo stimulation of intact human gut tissue is a valuable model to study nutritional effects on complex tissue systems. Furthermore, the consumption of coffee and roasting products may be able to induce nuclear NF-κB translocation in the human gut.

Advanced glycation endproducts (AGEs) accumulate on protein deposits including the beta-amyloid plaques in Alzheimer's disease. AGEs interact with the "receptor for advanced glycation endproducts", and transmit their signals using intracellular reactive oxygen species as second messengers. Ultimately, AGEs induce the expression of a variety of pro-inflammatory markers including the tumor necrosis factor (TNF-alpha) and inducible nitric oxide (NO) synthase. Antioxidants that act intracellularly, including polyphenols, have been shown to scavenge these "signaling" reactive oxygen species, and thus perform in an anti-inflammatory capacity. This study tested the pure compounds apigenin and diosmetin as well as extracts from silymarin, uva ursi (bearberry) and green olive leaf for their ability to attenuate AGE-induced NO and TNF-alpha production. All five tested samples inhibited BSA-AGE-induced NO production in a dose-dependent manner. Apigenin and diosmetin were most potent, and exhibited EC(50) values approximately 10 microM. In contrast, TNF-alpha expression was only reduced by apigenin, diosmetin and silymarin; not by the bearberry and green olive leaf extracts. In addition, the silymarin and bearberry extracts caused significant cell death at concentrations >or=10 microg/mL and >or=50 microg/mL, respectively. In conclusion, we suggest that plant-derived polyphenols might offer therapeutic opportunities to delay the progression of AGE-mediated and receptor for advanced glycation endproducts-mediated neuro-inflammatory diseases including Alzheimer's disease.

In many chronic neurodegenerative diseases including Frontotemporal Dementia and Alzheimer's disease (AD), microglial activation is suggested to be involved in pathogenesis or disease progression. Activated microglia secrete a variety of cytokines, including interleukin-1beta, interleukin-6, and tumor necrosis factor as well as reactive oxygen and nitrogen species (ROS/RNS). ROS and RNS contribute to alterations in neuronal glucose uptake, inhibition of mitochondrial enzymes, a decrease in mitochondrial membrane potential, impaired axonal transport, and synaptic signaling. In addition, ROS act as signaling molecules in pro-inflammatory redox-active signal transduction pathways. To establish a high throughput screening system for anti-inflammatory and neuroprotective compounds, we have constructed an "Enhanced Green Fluorescent protein" (EGFP) expressing neuronal cell line and set up a murine microglia/neuron co-culture system with these EGFP expressing neuronal cells. We show that microglia activation leads to neuronal cell death, which can be conveniently measured by loss of neuronal EGFP fluorescence. Moreover, we used this system to test selected polyphenolic compounds for their ability to downregulate inflammatory markers and to protect neurons against microglial insult. We suggest that this system might allow accelerated drug discovery for the treatment of inflammation-mediated neurodegenerative diseases.

Transfection of mammalian cell lines is a widely used technique that requires significant optimization, including transfection method or product used, DNA vector, cell density, media composition and incubation time. Generation and isolation of stable transfectants from the large pool of untransfected or only transiently transfected cells can be laborious and time-consuming. Transfection of DNA is usually performed with a non-linearized plasmid, since it is assumed that cutting the plasmid beforehand leads to a lower efficiency of transfection or the degradation of linearized DNA by cytosolic nucleases. However, the transfected circular plasmid will be linearized by a random cut within the cell and it might be possible that sensitive parts of the plasmid such as the resistance gene or the gene of interest are destroyed upon linearization. On the other hand, linearizing a plasmid before transfection by a single, defined cut with a selected restriction enzyme in a non-coding area of the gene has the advantage of ensuring the integrity of all necessary gene elements of the plasmid. In this study, we have compared these different methods in order to increase both transient and stable transfection efficiency in mammalian cells. We report that linearization of plasmid DNA prior to transfection can increase both the efficiency of stable clone generation and target gene expression, but is dependant on the site of linearization within the vector.

The cytotoxic activity of Maillard reaction products and coffee was studied using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay and the neutral red uptake (NRU) assay. Equimolar mixtures of sugars and lysine were heated at 120 degrees C and used to stimulate bovine aorta endothelial cells for 24 h. The cytotoxic activity increased with increase in educt concentration and heating time. Mixtures containing ribose were most active, followed by lactose and glucose. Hydrogen peroxide, which was present in the Maillard mixtures in concentrations between 7 and 87 microM, was identified as one of their major cytotoxic components. H2O2-concentrations increased further up to 130 microM under cell culture conditions. Filter coffee, espresso, and green coffee extract reduced cell viability significantly to 10, 19, and 83% of PBS-treated control. The effect was largely attenuated by the addition of catalase. Nil, 33, and 41 microM H2O2 was measured in green coffee extract, filter coffee, and espresso, respectively, increasing to 13, 369, and 333 microM during cell culture conditions. No additional H2O2 formation was detected when coffee was incubated for up to 5 h without further treatment. In conclusion, hydrogen peroxide is a major product in Maillard mixtures and coffee inducing cell death in vitro.

Synthetic peptides, 12-22 amino acid residues long, comprising the presumed coupling sites of the beta-adrenergic receptor with the stimulatory guanine-nucleotide-binding regulatory protein (Gs), were examined for their ability to modulate Gs activation in turkey erythrocyte membranes. Three peptides corresponding to the second cytoplasmic loop, the N-terminal region of the third cytoplasmic loop, and the N-terminal region of the putative fourth cytoplasmic loop, compete synergistically with the hormone-stimulated receptor for Gs activation with median effector concentrations of 15-35 microM, or 3-4 microM for combinations of two peptides. One peptide, corresponding to the C-terminal region of the third cytoplasmic loop, carries the unique ability to activate the Gs-adenylate-cyclase complex independent of the signalling state of the receptor. These observations are consistent with a dynamic model of receptor-mediated G-protein activation in membranes, where domains composed of the second, third and fourth intracellular loop of the receptor bind to and are interactive with the G-protein heterotrimer, resulting in ligand-induced conformational changes of the receptor. In response to hormone binding, the extent or the number of sites involved in interaction with Gs may be readjusted using a fourth site. Modulation of coupling sites may elicit congruent conformational changes within the Gs heterotrimer, with qualitatively different effects on GTP/GDP exchange in the alpha subunit of Gs and downstream effector regulation. This model corroborates and expands a similar model suggested for activated rhodopsin-transducin interaction [König, B., Arendt, A., McDowell, J. H., Kahlert, M., Hargrave, P. A.Hofmann, K. P. (1989) Proc. Natl Acad. Sci. USA 86, 6878-6882].

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that destroys patient memory and cognition, communication ability with the social environment and the ability to carry out daily activities. Despite extensive research into the pathogenesis of AD, a neuroprotective treatment - particularly for the early stages of disease - remains unavailable for clinical use. In this review, we advance the suggestion that lipoic acid (LA) may fulfil this therapeutic need. A naturally occurring cofactor for the mitochondrial enzymes pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, LA has been shown to have a variety of properties which can interfere with the pathogenesis or progression of AD. For example, LA increases acetylcholine (ACh) production by activation of choline acetyltransferase and increases glucose uptake, thus supplying more acetyl-CoA for the production of ACh. LA chelates redox-active transition metals, thus inhibiting the formation of hydroxyl radicals and also scavenges reactive oxygen species (ROS), thereby increasing the levels of reduced glutathione. In addition, LA down-regulates the expression of redox-sensitive pro-inflammatory proteins including TNF and inducible nitric oxide synthase. Furthermore, LA can scavenge lipid peroxidation products such as hydroxynonenal and acrolein. In human plasma, LA exists in an equilibrium of free and plasma protein bound form. Up to 150 muM, it is bound completely, most likely binding to high affinity fatty acid sites on human serum albumin, suggesting that one large dose rather than continuous low doses (as provided by "slow release" LA) will be beneficial for delivery of LA to the brain. Evidence for a clinical benefit for LA in dementia is yet limited. There are only two published studies, in which 600 mg LA was given daily to 43 patients with AD (receiving a standard treatment with choline-esterase inhibitors) in an open-label study over an observation period of up to 48 months. Whereas the improvement in patients with moderate dementia was not significant, the disease progressed extremely slowly (change in ADAScog: 1.2 points=year, MMSE: -0.6 points=year) in patients with mild dementia (ADAScog

Hydrogen peroxide has been shown to act as a second messenger mediating intracellular redox-sensitive signal transduction. Here we show that hydrogen peroxide is also able to transmit pro-inflammatory signals from one cell to the other and that this action can be inhibited by extracellularly added catalase. If these data can be further substantiated, hydrogen peroxide might become as important as nitric oxide as a small molecule intercellular (first) messenger.

Re-expression of cell cycle related genes such as cyclin-dependent kinases (cdk), cyclins, or cdk inhibitors in differentiated neurons in Alzheimer's disease (AD) is rooted in aberrant mitogenic signaling. Since microglia and astroglia proliferate in the vicinity of amyloid plaques, it is likely that plaque components or factors secreted from plaque-activated glia induce mitogenic signaling in neurons. Mitogenic compounds might be S100B, overexpressed by activated astrocytes, or advanced glycation end products (AGEs), a component of plaques. Both S100B and AGEs may interact with the multiligand receptor for AGEs (RAGE) and trigger for the activation of the p42/44 mitogen-activated protein kinase (p42/44 MAPK), whether they also count for cell cycle related signaling in neurons remains unresolved. By immunohistochemical staining, we confirmed that cyclin D(1) positive neurons are surrounded by AGE deposits, demonstrating the potential relevance in vivo. For exploring the mitogenic signal cascade, we used Neuro2a cells overexpressing human full-length RAGE (FL-RAGE) or the cytosolic deletion mutant (Delta-RAGE). In both cell lines, S100B and AGEs induced the production of reactive oxygen species but not in a RAGE-dependent manner. By contrast, in FL-RAGE cells but not in Delta-RAGE cells S100B and AGEs activate p42/44 MAPK, augment cyclin D(1)/cdk4 protein and RNA levels and the transition into the S-phase. Moreover, in FL-RAGE cells, decreased protein levels of the cdk inhibitor p16 were observed, and the p42/44 MAPK inhibitor UO126 prevented AGE and S100B stimulated cyclin D(1) expression and hindered cells to enter the S-phase. Our results demonstrate that S100B and AGE may serve as mitogenic sources for the stimulation of neurons to progress through the cell cycle whereby signaling proceeds via RAGE --p42/44 MAPK --cyclin D(1)/cdk4.

Oxidative stress and neuronal energy depletion are characteristic biochemical hallmarks of Alzheimer’s disease (AD). It is therefore conceivable that pro-energetic and antioxidant drags such as α-lipoic acid might delay the onset or slow down the progression of the disease. In a previous study, 600 mg α-lipoic acid was given daily to nine patients with AD (receiving a standard treatment with choline-esterase inhibitors) in an open-label study over an observation period of 12 months. The treatment led to a stabilization of cognitive functions in the study group, demonstrated by constant scores in two neuropsychological tests (the mini mental state exam, MMSE and the Alzheimer’s disease assessment score cognitive subscale, ADAScog). In this report, we have extended the analysis to 43 patients over an observation period of up to 48 months. In patients with mild dementia (ADAScog < 15), the disease progressed extremely slowly (ADAScog: +1.2 points/year, MMSE:-0.6 points/year), in patients with moderate dementia at approximately twice the rate. However, the progression appears dramatically lower than data reported for untreated patients or patients on choline-esterase inhibitors in the second year of long-term studies. Despite the fact that this study was not double-blinded, placebo-controlled and randomized, our data suggest that treatment with α-lipoic acid might be a successful ‘neuroprotective’ therapy option for AD. However, a state-of-the-art phase II trial is needed urgently.

Accumulation of hyperphosphorylated Tau protein as paired helical filaments in pyramidal neurons is a major hallmark of Alzheimer disease. Besides hyperphosphorylation, other modifications of the Tau protein, such as cross-linking, are likely to contribute to the characteristic features of paired helical filaments, including their insolubility and resistance against proteolytic degradation. In this study, we have investigated whether the four reactive carbonyl compounds acrolein, malondialdehyde, glyoxal, and methylglyoxal accelerate the formation of Tau oligomers, thioflavin T-positive aggregates, and fibrils using wild-type and seven pseudophosphorylated mutant Tau proteins. Acrolein and methylglyoxal were the most reactive compounds followed by glyoxal and malondialdehyde in terms of formation of Tau dimers and higher molecular weight oligomers. Furthermore, acrolein and methylglyoxal induced the formation of thioflavin T-fluorescent aggregates in a triple pseudophosphorylation-mimicking mutant to a slightly higher degree than wild-type Tau. Analysis of the Tau aggregates by electron microscopy study showed that formation of fibrils using wild-type Tau and several Tau mutants could be observed with acrolein and methylglyoxal but not with glyoxal and malondialdehyde. Our results suggest that reactive carbonyl compounds, particularly methylglyoxal and acrolein, could accelerate tangle formation in vivo and that this process could be slightly accelerated, at least in the case of methylglyoxal and acrolein, by hyperphosphorylation. Interference with the formation or the reaction of these reactive carbonyl compounds could be a promising way of inhibiting tangle formation and neuronal dysfunction in Alzheimer disease and other tauopathies.

Advanced glycation endproducts (AGEs) arise in vivo from the reaction of proteins with sugars or dicarbonyl compounds. They are thought to be involved in the pathogenesis of several diseases such as atherosclerosis, diabetes mellitus, renal failure, and Alzheimer's disease (AD). Several binding molecules for AGEs have been described and it is assumed that many of the effects of AGEs are mediated by receptors like the receptor for AGEs (RAGE). AGEs are known to induce the release of inflammatory cytokines from activated glia in the AD brain and thus AGEs affect the cell viability of neurons and glia. In cell culture experiments controversial effects of AGEs on cell growth and viability were reported by different research groups ranging from stimulation to inhibition of the cell viability. In the present study, the effect of in vitro prepared highly modified AGEs on the viability and the membrane integrity of cultured brain cells was investigated. Three different brain cell lines were treated with glucose human serum albumin AGEs (Glc-AGEs) and methyl glyoxal human serum albumin AGEs (MG-AGEs). To investigate the effect of these model AGEs on cell viability the CellTiter Blue (CTB) and the tetrazolium (3-[4,5-dimethylthioazol-2-yl]-2,5-diphenyl tetrazolium bromide) (MTT) were used. The membrane integrity after exposure to AGEs was assayed using the lactate dehydrogenase (LDH) assay. When using the CTB assay for evaluation all AGEs were found to reduce the viability compared with the native protein in all three cell lines. Additionally, all AGEs were found to affect the membrane integrity compared with the native protein in all cell lines. When using the MTT assay for evaluation only MG-AGEs were found to cause a decrease in the viability in all cell lines used. The results of the MTT assay in Glc-AGEs treated cells varied between the cell lines. To gain a deeper understanding of the cellular responses after exposure of cells to AGEs, the present study compares results obtained when using the CTB, the MTT or the LDH assay in identically AGE treated cells.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that destroys patient memory and cognition, communication ability with the social environment and the ability to carry out daily activities. Despite extensive research into the pathogenesis of AD, a neuroprotective treatment - particularly for the early stages of disease - remains unavailable for clinical use. In this review, we advance the suggestion that lipoic acid (LA) may fulfil this therapeutic need. A naturally occurring precursor of an essential cofactor for mitochondrial enzymes, including pyruvate dehydrogenase (PDH) and alpha-ketoglutarate dehydrogenase (KGDH), LA has been shown to have a variety of properties which can interfere with pathogenic principles of AD. For example, LA increases acetylcholine (ACh) production by activation of choline acetyltransferase and increases glucose uptake, thus supplying more acetyl-CoA for the production of ACh. LA chelates redox-active transition metals, thus inhibiting the formation of hydroxyl radicals and also scavenges reactive oxygen species (ROS), thereby increasing the levels of reduced glutathione. Via the same mechanisms, downregulation redox-sensitive inflammatory processes is also achieved. Furthermore, LA can scavenge lipid peroxidation products such as hydroxynonenal and acrolein. The reduced form of LA, dihydrolipoic acid (DHLA), is the active compound responsible for most of these beneficial effects. R-alpha-LA can be applied instead of DHLA, as it is reduced by mitochondrial lipoamide dehydrogenase, a part of the PDH complex. In this review, the properties of LA are explored with particular emphasis on how this agent, particularly the R-alpha-enantiomer, may be effective to treat AD and related dementias.

In Alzheimer's disease (AD), in aging, and under conditions of oxidative stress, the levels of reactive carbonyl compounds continuously increase. Accumulating carbonyl levels might be caused by an impaired enzymatic detoxification system. The major dicarbonyl detoxifying system is the glyoxalase system, which removes methylglyoxal in order to minimize cellular impairment. Although a reduced activity of glyoxalase I was evident in aging brains, it is not known how raising the intracellular methylglyoxal level influences neuronal function and the phosphorylation pattern of tau protein, which is known to be abnormally hyperphosphorylated in AD. To simulate a reduced glyoxalase I activity, we applied an inhibitor of glyoxalase I, p-bromobenzylglutathione cyclopentyl diester (pBrBzGSCp(2)), to SH-SY5Y neuroblastoma cells to induce chronically elevated methylglyoxal concentrations. We have shown that 10 microM pBrBzGSCp(2) leads to a fourfold elevation of the methylglyoxal level after 24 hr. In addition, glyoxalase I inhibition leads to reduced cell viability, strongly retracted neuritis, increase in [Ca(2+)](i), and activation of caspase-3. However, pBrBzGSCp(2) did not lead to tau "hyper"-phosphorylation despite activation of p38 mitogen-activated protein kinase and c-Jun NH(2)-terminal kinase but rather activated protein phosphatases 2 and induced tau dephosphorylation at the Ser(202)/Thr(205) and Ser(396)/Ser(404) epitopes. Preincubation with the carbonyl scavenger aminoguanidine prevented tau dephosphorylation, indicating the specific effect of methylglyoxal. Also, pretreatment with the inhibitor okadaic acid prevented tau dephosphorylation, indicating that methylglyoxal activates PP-2A. In summary, our data suggest that a reduced glyoxalase I activity mimics some changes associated with neurodegeneration, such as neurite retraction and apoptotic cell death.

The accumulation of advanced glycation end products (AGEs) in brains with Alzheimer's disease (AD) has been implicated in the formation of insoluble deposits such as amyloid plaques and neurofibrillary tangles. AGEs are also known to activate glia, resulting in inflammation and neuronal dysfunction. As reactive intermediates of AGE formation, neurotoxic reactive dicarbonyl compounds such as glyoxal and methylglyoxal have been identified. One of the most effective detoxification systems for methylglyoxal and glyoxal is the glutathione-dependent glyoxalase system, consisting of glyoxalase I and glyoxalase II. In this study, we have determined the methylglyoxal and glyoxal levels in the cerebrospinal fluid of AD patients compared to healthy controls. Methylglyoxal levels in AD patients were twofold higher than in controls, but this difference was not significant due to the large intergroup variations and the small sample size. However, the concentrations of both compounds were five to seven times higher in CSF than in plasma. We also investigated the glyoxalase I level in AD and healthy control brains. The number of glyoxalase I- positive neurons were increased in AD brains compared to controls. Our findings suggest that glyoxalase I is upregulated in AD in a compensatory manner to maintain physiological methylglyoxal and glyoxal levels.

Methylglyoxal (MG) is a reactive alpha-ketoaldehyde physiologically generated as a by-product of glycolysis. MG that is able to form protein adducts resulting in advanced glycation end products accumulates under conditions associated with neurodegeneration such as impaired glucose metabolism or oxidative stress. In the present study, short-term exposure of human neuroblastoma SH-SY5Y cells to MG was associated with an early depolarization of the plasma membrane, glutamate release, and formation of reactive oxygen species. In addition, long-term exposure (24 h) of SH-SY5Y cells to MG caused a decrease in cell viability, intracellular ATP, and rhodamine 123 (Rh-123) fluorescence. ATP depletion and the decrease in Rh-123 fluorescence were prevented by carbonyl scavengers, the nitric oxide synthase inhibitor L-NAME, and N-methyl-d-aspartate (NMDA) receptor antagonists. Furthermore, the MG-induced glutamate release and the loss in cell viability were prevented by NMDA receptor antagonists. Therefore, MG renders cells more vulnerable to excitotoxicity. In conclusion, carbonyl scavengers as well as NMDA receptor antagonists may represent effective therapeutic tools to reduce the risk of pathophysiological changes associated with carbonyl stress in neurodegenerative diseases.

Increased modification and crosslinking of proteins by advanced glycation end products (AGEs) is a characteristic feature of aging, and contributes to the formation of many of the lesions of neurodegenerative diseases including neurofibrillary tangles and amyloid plaques in Alzheimer's disease. Therefore, defense mechanisms against AGE formation or detoxification of their precursors such as the glyoxalase system are of particular interest in aging research. Thus, we investigated the age-dependent protein expression, the activity as well as the RNA level of glyoxalase I in Brodmann area 22 (auditory association area of superior temporal gyrus) of the human cerebral cortex. Our immunohistochemical results demonstrate the localization of glyoxalase I in neurons, predominantly pyramidal cells, as well as in astroglia, located predominantly in the subpial region. The number of glyoxalase I expressing neurons and astroglia increases with age, with a peak at approximately 55 years, and progressively decreases thereafter. These results were confirmed by biochemical investigations in total brain tissue, where the RNA, the protein level as well as the activity of glyoxalase I enzyme were analyzed in different age groups. In conclusion, the increase in glyoxalase I expression up to the age of 55 may be a compensatory mechanism against high oxoaldyde levels and the accumulation of AGEs. However, the decline of glyoxalase expression and activity in old age, possibly caused by impairment in transcription or/and translation, may subsequently lead to increased levels of reactive carbonyl compounds, followed by protein crosslinking, inflammation, oxidative stress and neuronal degeneration.

Renal accumulation of AGEs may contribute to the progression of diabetic nephropathy. We evaluated the effect of ramipril (a pure ACE inhibitor) and AVE7688 (a dual inhibitor of ACE and neutral endopeptidase) on renal accumulation of the advanced glycation end-product (AGE) 3-deoxyglucosone-imidazolone, carboxymethyllysine (CML) and pentosidine, and on clearance of CML in type 2 diabetes.Male Zucker diabetic fatty rats (ZDF, Gmi-fa/fa) rats were treated from age 10 to 37 weeks with ramipril (1 mg.kg(-1).day(-1)), AVE7688 (45 mg.kg(-1).day(-1)) or without drug. Ramipril and AVE7688 reduced albuminuria by 30 and 90%, respectively.ZDF rats showed increased renal accumulation of the AGE subtypes 3-deoxyglucosone-imidazolone, pentosidine and CML by about 40, 55 and 55%, respectively compared with heterozygous, non-diabetic control animals at the age of 37 weeks. AVE7688 but not ramipril attenuated the renal accumulation of 3-deoxyglucosone-imidazolone, pentosidine and CML and improved CML clearance in ZDF rats. During glycation reactions in vitro, AVE7688 also demonstrated potent chelating activity and inhibited metal-catalysed formation of pentosidine and CML.Improved AGE clearance and direct inhibition of AGE formation by chelation may contribute to reduced accumulation of renal AGEs and to the nephroprotective effects of vasopeptidase inhibition in type 2 diabetes.

Advanced glycation end products (AGEs) are known to be involved in the pathogenesis of several diseases and therefore effects of AGEs on cells are the objective of numerous investigations. Since AGEs used in biochemical studies are usually not chemically characterized, comparison of data is difficult if not impossible. To find a suitable characterization protocol, human serum albumin was reacted with different concentrations of glucose, methyl glyoxal, and glyoxylic acid. The obtained AGEs were characterized with respect to the extent of side chain modifications (lysine and arginine), the carboxymethyl lysine and carbonyl content, and the fibrillar state. Additionally, their fluorescence and absorbance characteristics were extensively studied. Although we found significant differences in the degree of modification and in AGE-specific fluorescence when using different modifiers, the results provide important information and allow comparing AGEs derived from different modifier concentrations. The results also suggest strong conformational changes within the modified proteins. In the present paper we propose a set of parameters that is sufficient to partially characterize AGEs used for biochemical studies.

Alzheimer's disease is the most common cause of dementia in the elderly population. The most widely used treatment for Alzheimer's disease at present is acetylcholinesterase inhibitors, which aim to prolong cognitive function through increased synaptic activity, without providing neuroprotection. This treatment is only symptomatic and provides modest outcomes for patients. The recent elucidation of the inflammatory pathways involved in Alzheimer's disease however, has opened doors for better treatment and prevention by identification of areas of therapeutic intervention that target the cause of the disease rather than the symptoms. This review describes the inflammatory pathways that are thought to be present in Alzheimer's disease and some of the new therapies that have shown promise, via alteration or inhibition of these pathways. Some of the therapies included in this review, which have already demonstrated beneficial effects in the treatment of Alzheimer's disease, or have the potential to do so, are nonsteroidal anti-inflammatory drugs, statins, RAGE antagonists and antioxidants.

Advanced glycation endproducts (AGEs) accumulate on long-lived proteins, including β-amyloid plaques in Alzheimer's disease, and are suggested to contribute to neuronal dysfunction and cell death. We have investigated the effects of a model AGE upon glucose metabolism and energy production in a neuroblastoma cell line. AGEs decrease cellular ATP levels and increase glucose consumption and lactate production. All of the AGE-induced metabolic changes can be attenuated by antioxidants such as (R+)-α-lipoic acid and 17β-estradiol. These antioxidants may become useful drugs against (AGE-mediated) effects in neurodegeneration through their positive effects on cellular energy metabolism.

Alzheimer: The Life of a Physician& the Career of a Disease by Konrad Maurer and Ulrike Maurer Columbia University Press New York, New York, USA 256 pages, US $49.50 ISBN 0 231 11896 1 ![][1] The very name ‘Alzheimer’ now sends shudders down the spine. Not through any fault of the pioneering psychiatrist who first described the disease that now bears his name, but because of the mental devastation that accompanies this increasingly common malady. If no cure or preventive treatment is found, 5% of the total population will suffer from the disease by the year 2050. Despite considerable progress in histochemical, biochemical and genetic research, the underlying causes of Alzheimer's disease (AD) remain mysterious, as did, until recently, the man after whom it was named. Now, a new book by Konrad Maurer, Director of the Psychiatric University Clinic in Frankfurt, Germany, and his wife Ulrike, gives us some insight into Alzheimer's life. But Alzheimer: The Life of a Physician & the Career of a Disease is more than a biography; it is a story of scientific discovery at a crucial stage in the history of biological psychiatry … [1]: /embed/graphic-1.gif

Deposition of cross-linked insoluble protein aggregates such as amyloid plaques is characteristic for Alzheimer's disease. Microglial activation by these extracullar deposits has been proposed to play a crucial role in functional degeneration as well as cell death of neurones. A sugar-derived post-translational modification of long-lived proteins, advanced glycation endproducts (AGEs), activate specific signal transduction pathways, resulting in the up-regulation of various pro-inflammatory signals such as cytokines [interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF-alpha)] and inducible nitric oxide synthase (iNOS). Our goal was to study AGE-activated signal transduction pathways involved in the induction of pro-inflammatory effectors in the murine microglial cell line N-11. Chicken egg albumin-AGE (CEA-AGE), used as model AGE, induces nitric oxide (NO), TNF-alpha and IL-6 production. The AGE receptor, RAGE, and the transcription factor, nuclear factor kappa B (NF-kappaB), appear to be involved in all pathways, since a neutralizing RAGE antibody and a peptide inhibiting NF-kappaB translocation down-regulated NO, TNF-alpha and IL-6 production. NO and TNF-alpha, but not IL-6 production appear to be regulated independently, since NOS inhibitors did not decrease TNF-alpha secretion and a neutralizing TNF-alpha antibody did not reduce NO production, while employment of NOS inhibitors reduced significantly the secretion of IL-6. Inhibition of the MAP-kinase-kinase (MEK) and phosphatidylinositol 3-kinase (PI3K) pathway, but not that of mitogen-activated protein kinase-p38 (MAPK-p38), reduced NO, TNF-alpha and IL-6 significantly, suggesting that simultaneous activation of the first two pathways is necessary for the AGE-induced induction of these pro-inflammatory stimuli.

OBJECTIVE—Advanced glycation end products (AGEs) are a complex and heterogenous group of proteins that are formed by nonenzymatic glycation in a series of reactions. It is hypothesized that they may play a role in the pathogenesis of diabetes-related complications; at present, however, their exact biological role is scarcely understood. Clinical studies so far have shown that serum levels of AGEs are correlated with clinical stages of diabetes complications such as retinopathy and nephropathy. This study was performed in children and adolescents with type 1 diabetes to examine the putative role of serum AGEs in respect to metabolic control and diabetes complications in relation to a number of clinical and laboratory parameters. RESEARCH DESIGN AND METHODS—We studied 99 children and adolescents up to the age of 20 years with type 1 diabetes and 60 control subjects. Serum levels of AGEs were measured with two different methods [fluorescence spectroscopy and Nε-(carboxymethyl)lysine (CML) enzyme-linked immunosorbent assay] and correlated with clinical data, such as age, diabetes duration, BMI, and long-term metabolic control determined by HbA1c, and laboratory parameters, such as serum lipids. RESULTS—Serum levels of fluorescent AGEs, but not of CML-AGEs, in children and adolescents with type 1 diabetes were significantly higher compared with control subjects. There was an age-dependent increase of fluorescent AGEs in children and adolescents with diabetes that was not seen in healthy children and adolescents. Levels of fluorescent AGEs in patients with diabetes between 13 and 16 years of age correlated positively with HbA1c levels. No significant association between levels of AGEs and diabetes duration was found. Children and adolescents with diabetes and high serum triglycerides had significantly higher serum levels of fluorescent AGEs. Children and adolescents with diabetes between the age of 13 and 16 years with high levels of LDL had significantly higher levels of fluorescent AGEs. CONCLUSIONS—In this study we demonstrated a clear age-dependent increase of fluorescent AGEs but not of CML-AGEs in children and adolescents with diabetes type 1. Moreover we showed a strong association between serum AGEs and serum triglycerides and cholesterol. The observed effect may be caused by a loss of optimal regulation of lipid metabolism. It could suggest a link between triglycerides and formation of AGEs. This new and interesting finding and its impact on metabolic control and the development of diabetes complications should be examined in the future.

Increased expression and altered processing of the amyloid precursor protein (APP) and generation of beta-amyloid peptides is important in the pathogenesis of amyloid plaques in Alzheimer's disease (AD). Transgenic Tg2576 mice overexpressing the Swedish mutation of human APP exhibit beta-amyloid deposition in the neocortex and limbic areas, accompanied by gliosis and dystrophic neurites. However, murine plaques appear to be less cross-linked and the mice show a lower degree of inflammation and neurodegeneration than AD patients. 'Advanced glycation endproducts (AGEs)', formed by reaction of proteins with reactive sugars or dicarbonyl compounds, are able to cross-link proteins and to activate glial cells, and are thus contributing to plaque stability and plaque-induced inflammation in AD. In this study, we analyze the tissue distribution of AGEs and the pro-inflammatory cytokines IL-1beta and TNF-alpha in 24-month-old Tg2576 mice, and compare the AGE distribution in these mice with a younger age group (13 months old) and a typical Alzheimer's disease patient. Around 70% of the amyloid plaque cores in the 24-month-old mice are devoid of AGEs, which might explain their solubility in physiological buffers. Plaque associated glia, which express IL-1beta and TNF-alpha, contain a significant amount of AGEs, suggesting that plaques, i.e. Abeta as its major component, can induce intracellular AGE formation and the expression of the cytokines on its own. In the 13-month-old transgenic mice, AGEs staining can neither be detected in plaques nor in glial cells. In contrast, AGEs are present in high amounts in both plaques and glia in the human AD patient. The data obtained in this show interesting differences between the transgenic mouse model and AD patients, which should be considered using the transgenic approach to test therapeutical strategies to eliminate plaques or to attenuate the inflammatory response in AD.

Beta-amyloid peptide (Abeta) and "Advanced glycation endproducts" (AGEs) are components of the senile plaques in Alzheimer's disease patients. It has been proposed that both AGEs and Abeta exert many of their effects, which include the upregulation of pro-inflammatory cytokines, through RAGE ("receptor for advanced glycation endproducts"). To investigate whether Abeta and AGEs cause similar or identical effects on cell survival and energy metabolism, we have compared the effects of a model-AGE and Abeta on cell viability, ATP level, glucose consumption and lactate production in the neuroblastoma cell line SH-SY5Y. The results show that AGEs and Abeta increase glucose consumption and decrease ATP levels in a dose dependent manner. Furthermore, both compounds decrease mitochondrial activity measured by the MTT assay. However, only AGEs decrease the number of cells and significantly increase lactate production. These data indicate that both AGEs and Abeta can cause differential disturbances in neuronal metabolism, which may contribute to the pathophysiological findings in Alzheimer's disease. However, their signalling pathways are apparently quite distinct, a fact which should stimulate a more detailed investigation in this field, e.g. for the purpose of a rational design of potential "neuroprotective" RAGE antagonists.

beta-Amyloid (Abeta) plaques are characteristic hallmarks of Alzheimer's disease (AD). In AD, it has been suggested that activation of microglial cells might be the link between Abeta deposition and neuronal degeneration. Activated microglia are associated with senile plaques and produce free radicals and inflammatory cytokines. However, it is still not clear whether Abeta needs a prestimulated environment to exert its proinflammatory potential. Advanced glycation endproducts (AGEs), protein-bound oxidation products of sugars, have been shown to accumulate in senile plaques and could induce a silent but chronic inflammation in the AD brain. We tested whether Abeta acts as an amplifier of a submaximal proinflammatory response initiated by exposure to chicken egg albumin-AGE, lipopolysaccharide or interferon-gamma. Synthetic Abeta was used to produce three different samples (Abeta-fibrilar; Abeta-aggregated; Abeta-AGE), which were characterized for beta-sheeted fibrils by the thioflavin-T test and electron microscopy. As markers of microglial activation, nitric oxide, interleukin-6, macrophage-colony stimulation factor and tumour necrosis factor-alpha production was measured. All three Abeta samples alone could not induce a detectable microglial response. The combination of Abeta preparations, however, with the coinducers provoked a strong microglial response, whereby Abeta-AGE and fibrilar Abeta were more potent inflammatory signals than aggregated Abeta. Thus, Abeta in senile plaques can amplify microglial activation by a coexisting submaximal inflammatory stimulus. Hence, anti-inflammatory therapeutics could either target the primary proinflammatory signal (e.g. by limiting AGE-formation by AGE inhibitors or cross-link breakers) or the amplifyer Abeta (e.g. by limiting Abeta production by beta- or gamma-secretase inhibitors).

A new therapeutic approach is being developed for the treatment of Alzheimer's disease (AD). This approach involves the deliberate induction of an autoimmune response to amyloid-beta (Abeta) peptide, the constituent of neuritic plaques that is thought to cause the neurodegeneration and dementia in AD. If this approach is to be effective, antibodies must be produced that can selectively target the toxic forms of Abeta, while leaving the functionally-relevant forms of Abeta and its precursor protein untouched. Furthermore, an approach needs to be found that avoids provoking an acute neuroinflammatory response. The situation is made even more challenging by uncertainty regarding which isoforms of Abeta contribute to the pathogenesis of AD.

Advanced glycation endproducts (AGEs), sugar-derived protein modifications and lipid peroxidation products are prominent features of Alzheimer's disease. AGEs accumulate on beta-amyloid plaques during the course of the disease and can exert chronic oxidative stress via receptor-mediated mechanisms. Lipid peroxidation products such as hydroxynonenal, further markers of oxidative stress, are also increased in Alzheimer's diesease. In this study we present evidence for a direct biochemical link between AGEs and lipid peroxidation. Our results show that AGEs induce lipid peroxidation in a neuronal cell line in a dose-dependant manner, and that blocking the specific AGE-receptor RAGE, as well as using different antioxidants (alpha-lipoic acid, N-acetylcysteine, 17 beta-estradiol or aminoguanidine) can reduce the AGE-mediated formation of lipid peroxidation products. Thus, both RAGE antagonists and scavengers of oxygen free radicals could be useful in protecting brain tissue from lipid peroxidation and its pathophysilogical consequences that occur in Alzheimer's disease.

In Alzheimer’s disease, neurons in affected regions re-enter the cell cycle, leave the G0 state and appear to be arrested at both the G1/S and G2/M phase with resulting cell death, predominantly by apoptosis. Further hallmarks of AD are crosslinked protein deposits (amyloid plaques and neurofibrillary tangles), which time-dependently become modified by “advanced glycation endproducts (AGEs)”. Since AGEs activate both mitogenic and redox-sensitive pathways, they might be involved both in cell cycle re-entry and arrest.

Various isoforms of the nitric oxide (NO) producing enzyme nitric oxide synthase (NOS) are elevated in Alzheimer's disease (AD) indicating a critical role for NO in the pathomechanism. NO can react with superoxide to generate peroxynitrite, a process referred to as oxidative stress, which is likely to play a role in AD. Peroxynitrite in turn, nitrates tyrosine residues to form nitrotyrosine which can be identified immunohistochemically. To study the potential structural link between the increased synthesis of NO and the deposition of nitrotyrosine in AD, we analyzed the expression of neuronal NOS (nNOS), inducible NOS (iNOS) and endothelial NOS (eNOS) in AD and control brain, and compared the localization with the distribution of nitrotyrosine. Nitrotyrosine was detected in neurons, astrocytes and blood vessels in AD cases. Aberrant expression of nNOS in cortical pyramidal cells was highly co-localized with nitrotyrosine. Furthermore, iNOS and eNOS were highly expressed in astrocytes in AD. In addition, double immunolabeling studies revealed that in these glial cells iNOS and eNOS are co-localized with nitrotyrosine. Therefore, it is suggested that increased expression of all NOS isoforms in astrocytes and neurons contributes to the synthesis of peroxynitrite which leads to generation of nitrotyrosine. In view of the wide range of isoform-specific NOS inhibitors, the determination of the most responsible isoform of NOS for the formation of peroxynitrite in AD could be of therapeutic importance in the treatment of Alzheimer's disease.

Recent immunological approaches have greatly helped understanding the significance of advanced glycation end products (AGEs) in age-related diseases. However, immunohistochemical localization of AGEs in tissues or their quantitative determination in biological fluids sometimes yields inconsistent results among different investigators. Since these differences might be caused by the heterogeneity of the AGE antibodies, a systematic mapping of their epitope recognition pattern would help in the evaluation of these different results. For this purpose, an N-terminally acetylated combinatorial dipeptide library with 400 positionally defined dipeptides was modified by glucose to yield AGEs, which are thought to be present on the protein side chains. Using this library, we have characterized six different AGE antibodies in respect to their immunoreactivity towards AGE-modified dipeptides. All antibodies predominantly recognized only one AGE-modified amino acid side chain (and not a particular dipeptide). In most cases, arginine- and lysine- derived AGEs, but also some epitopes on asparagine and on heterocyclic amino acids were recognized. Very interestingly, the immunization of different animals with the same antigen produced AGE antibodies with a totally different epitope recognition pattern. Defining the antigen recognition pattern with this method might help in the quality control of polyclonal AGE antibodies for immunodetection. In addition, defined AGE antibodies (as neutralizing antibodies) could also help to define “signal-active” AGEs in terms of specific AGE-mediated cellular responses.

Non-enzymatic glycation of proteins with reducing sugars and subsequent transition metal-catalyzed oxidations leads to the formation of protein-bound "advanced glycation endproducts" (AGEs). They accumulate on long-lived proteins including on and in the vicinity of the beta-amyloid plaques in Alzheimer's disease (AD). Since the AGE modification of a protein increases with time, and such a "long-term incubation" might also occur in the AD brain, we investigated whether an increase in the cytotoxic effects of an AGE-modified model protein occurs over time. Bovine serum albumin (BSA) was modified by glucose for defined time periods, and the viability of SH-SY5Y neuroblastoma cells, incubated with the differentially AGE-modified BSA samples, was measured with the MTT assay. Cytotoxicity of the AGE-modified BSAs increased in correlation to the incubation time with glucose. Among the AGE-specific markers, browning (OD 400) correlated best with cytotoxicity, followed by AGE-specific fluorescence and the defined AGE, carboxymethyllysine. Since AGEs accumulate in AD over time, they may be one of the "age-related" factors contributing to neuronal cell death in Alzheimer's disease.

Accumulation of Advanced Glycation Endproducts (AGEs) in the brain is a feature of ageing and degeneration, especially in Alzheimer’s disease (AD). Increased AGE levels explain many of the neuropathological and biochemical features of AD such as extensive protein crosslinking (β-amyloid and MAP-tau), glial activation, oxidative stress and neuronal cell death. Oxidative stress and AGEs initiate a positive feedback loop, where normal age-related changes develop into a pathophysiological cascade. Combined intervention using antioxidants, anti-inflammatory drugs and AGE-inhibitors may be a promising neuroprotective strategy.

The reaction of proteins with reducing sugars leads to the formation of 'advanced glycation endproducts' (AGEs). They accumulate in Alzheimer's disease brain in the vicinity of beta-amyloid plaques. AGEs are cytotoxic by a mechanism involving reactive oxygen species, which implies that they could compromise glutathione redox status. In this study, we show that AGEs (BSA-AGE and beta-amyloid-AGE) persistently increase the ratio of oxidized to reduced glutathione in a dose- and time-dependent manner in SH-SY5Y neuroblastoma cells. The level of oxidized glutathione accounted to 10-14% and persisted for up to 24 h in the presence of added AGEs. In contrast, the unmodified beta-amyloid peptides A beta (1-40) and A beta (25-35) had no significant effect on glutathione redox status. The AGE-induced increase in oxidized glutathione could be prevented by the radical scavengers N-acetylcysteine, alpha-lipoic acid and 17beta-estradiol or by application of catalase, indicating that superoxide and hydrogen peroxide production precedes the AGE-mediated depletion of reduced glutathione.

An excess of reactive carbonyl compounds (carbonyl stress) and their reaction products, advanced glycation endproducts (AGEs), are thought to play a decisive role in the pathogenesis of neurodegenerative disorders and Parkinson's disease (PD) in particular. Accumulation of AGEs in various intracellular pathological hallmarks of PD, such as Lewy bodies, densely crosslinked intracellular protein deposits formed from neurofilament components and alpha-synuclein, have already been described in patients in advanced stages of the disease. There is, however, no indication of the involvement of AGE-induced crosslinking of alpha-synuclein in very early stages of the disease. In this study, we observed that AGEs and alpha-synuclein are similarly distributed in very early Lewy bodies in the human brain in cases with incidental Lewy body disease. These cases might be viewed as pre-Parkinson patients, i.e. patients who came for autopsy before the possible development of clinical signs of PD. AGEs are both markers of transition metal induced oxidative stress as well as, inducers of protein crosslinking and free radical formation by chemical and cellular processes. Thus, it is likely that AGE promoted formation of Lewy bodies reflects very early causative changes rather than late epiphenomenons of PD.

The effect of the carbonyl compound glyoxal on the induction of advanced glycation end products (AGEs) in the fetal epithelial lung cells L132 was investigated using immunohistochemical, immunoelectron microscopic, and biochemical methods. It was found that glyoxal treatment resulted in morphological changes of the cells and in the membranous and cytosolic localization of AGEs such as methyl-glyoxal-derived compounds, N-(carboxymethyllysine) (CML) and imidazolone. The formation of AGEs was accompanied with a change in the intracellular expression of cathepsin D and a loss of enzymatic activity.

Non-enzymatic glycation of proteins with reducing sugars and subsequent transition metal catalysed oxidations leads to the formation of protein bound "advanced glycation endproducts" (AGEs). They accumulate on long-lived proteins and are for example structural components of the beta-amyloid plaques in Alzheimer's disease. Since the oxidation of glycated proteins as well as the interaction of AGEs with cell surface receptors produces superoxide radicals, it was tested in BHK 21 hamster fibroblast cells and SH-SY5Y human neuroblastoma cells if AGEs can exert cytotoxic effects on cells. Cell viability was assessed with three independent tests: MTT-assay (activity of the mitochondrial respiratory chain), lactate dehydrogenase assay (release of cytoplasmatic enzymes, membrane integrity) and Neutral Red assay (active uptake of a hydrophilic dye). Two model AGEs, chicken egg albumin-AGE and BSA-AGE, both caused significant cell death in a dose-dependent manner. The cytotoxic effects of AGEs could be attenuated by alpha-ketoglutarate and pyruvate, by antioxidants such as thioctic acid and N-acetylcysteine, and by aminoguanidine, an inhibitor of nitric oxide synthase. This suggests that reactive oxygen species as well as reactive nitrogen species contribute to AGE mediated cytotoxicity. Since AGEs accumulate on beta-amyloid plaques in AD over time, they may additionally contribute to oxidative stress, cell damage, functional loss and even neuronal cell death in the Alzheimer's disease brain.

Nonenzymatically glycated proteins and their advanced stage, the 'advanced glycation end products' (AGEs), have been detected in long-lived proteins and protein deposits in human and animal tissues. They are thought to be associated with normal aging and particularly with the pathogenesis of diabetic complications and Alzheimer's disease. AGEs accumulate in human neurons in an age-dependent manner and, in Alzheimer's disease patients, particularly in amyloid plaques and neurofibrillary tangles. In this study, we demonstrate AGE immunoreactivity in the canine brain, particularly in cerebellar Purkinje cells and brainstem neurons. In addition, distinct AGE-positive granules can be detected in the Purkinje cells which accumulate in an age-dependent manner. Staining with PAS and oil-red suggests that these AGE-positive granules contain the protein, but not the lipid constituents associated with lipofuscin. Our results show that the pattern of AGE distribution in the canine cerebellum resembles the situation in the human brain, but that the time course of AGE formation is much faster in dogs reflecting their much shorter life span.

Alzheimer's disease is a neurodegenerative disorder comprising multisystem atrophies probably caused by multifactorial processes. The disease is characterized by typical neuropathology, impaired synaptic function and massive cell loss. The pathobiochemistry of this disorder involves oxidative stress, which accumulates free radicals leading to excessive lipid peroxidation and neuronal degeneration in certain brain regions. Moreover, radical induced disturbances of DNA, proteins and lipid membranes have been measured. The hypothesis has been proposed that cellular events involving oxidative stress may be one basic pathway leading to neurodegeneration in Alzheimer's disease. In this work we report evidence for increased oxidative stress and disturbed defense mechanisms in Alzheimer's disease, which may result in a self-propagating cascade of neurodegenerative events. Furthermore it is evident from experimental data, that aggregation of beta-amyloid and beta-amyloid toxicity is favourably caused by oxidative stress. Therefore, oxidative stress plays a key role in the conversion of soluble to unsoluble beta-amyloid, suggesting that oxidative stress is primary to the beta-amyloid cascade.

Recent studies suggest that advanced glycation endproducts play an important role in cardiovascular complications of ageing, diabetes and end-stage renal failure. Since highly elevated levels of advanced glycation endproducts are present in serum of patients on maintenance haemodialysis, an accurate and rapid assay for their determination would be useful. This would be particularly valuable for monitoring the removal of advanced glycation endproducts by novel dialysis membranes, as well as the effect of new drugs for the inhibition of their formation. Measurement of advanced glycation endproducts in serum was performed by two competitive ELISAs, using a monoclonal antibody directed against imidazolone, an advanced glycation endproduct formed by the reaction of arginine with 3-deoxyglucosone, and a polyclonal antibody directed against keyhole limpet haemocyanin-advanced glycation endproduct, as well as by quantitative fluorescence spectroscopy. Each of the assays showed significant differences between the controls and the maintenance haemodialysis patients. Advanced glycation endproduct levels determined by each of the ELISAs correlated with total and protein-bound fluorescence, but not with each other, suggesting a variable distribution of advanced glycation endproducts on serum proteins among the maintenance haemodialysis patients.

Accumulation of advanced glycation endproducts (AGE) in the brain is a feature of ageing and degeneration, especially in Alzheimer's disease (AD). Increased AGE levels explain many of the neuropathological and biochemical features of AD such as extensive protein crosslinking (beta-amyloid and MAP-tau), oxidative stress and neuronal cell death. Oxidative stress and AGEs initiate a positive feedback loop, where normal age-related changes develop into a pathophysiological cascade. Combined intervention using antioxidants, metal chelators, anti-inflammatory drugs and AGE-inhibitors may be a promising neuroprotective strategy.

Demographische Betrachtungen. Der Altersaufbau der Bevolkerung Deutschlands hat sich im letzten Jahrhundert stark verandert. Nach koordinierten Vorausberechnungen halt dieser Trend an und es werden im Jahr 2030 die am starksten besetzten Altersjahrgange im siebten Lebensjahrzehnt zu finden sein (Bundesrat 1984, Sommer 1992). 1989 waren etwa drei Funftel der Bevolkerung der Bundesrepublik Deutschland zwischen 20 und 60 Jahren alt. Der Anteil der Jungeren und der Alteren betrug jeweils etwa ein Funftel. Im Jahre 2030 soll ein Drittel der Bevolkerung 60 Jahre oder alter sein. Die Entwicklung der Altersstruktur zur immer alter werdenden Bevolkerung bedingt weitreichende Konsequenzen fur viele Lebensbereiche. Mit Blick auf die Gesundheitsfursorge ist zu beachten, das alterskorrelierte chronische Erkrankungen uberproportional zunehmen werden. Eine besondere Herausforderung stellen Hirnabbauerkrankungen im Alter dar, die besonders pflegeintensiv sind. Bisher stehen fur die Therapie noch keine Strategien und Konzepte zur Verfugung, die als uberzeugend gelten konnen, da ausreichende Erkenntnisse zu Ursachen, Entstehungsbedingungen und verlaufsbestimmenden Faktoren noch nicht vorhanden sind.